1. Field of the Invention
The present invention relates to an electronic component including a laminate formed from a plurality of resin insulating layers, wherein internal electrodes are connected to external electrodes on end surfaces of the laminate.
2. Description of the Related Art
In general, an electronic component in which a laminate is formed by laminating, for example, resin insulating layers and a coil pattern and, in addition, the laminate is held between two magnetic substrates has been disclosed in the related art, for example, Japanese Unexamined Patent Application Publication No. 8-203737. In this case, internal electrodes connected to the coil pattern are exposed at end surfaces of the laminate. Furthermore, external electrodes are disposed on the end surfaces of the laminate by a sputtering method or the like and the external electrodes are connected to the exposed internal electrodes.
On the other hand, a configuration in which a conductor pad is disposed on an end surface of a laminate in such a way as to locate between an internal electrode and an external electrode is disclosed in the related art, for example, Japanese Unexamined Patent Application Publication No. 2006-287063. In this case, the conductor pad is formed by using the same material as that for the internal electrode and, in addition, has a predetermined area larger than the end surface area of the internal electrode and smaller than the end surface area of the external electrode. Consequently, the conductor pad is configured to enhance the electrical connectivity between the internal electrode and the external electrode.
Incidentally, the linear expansion coefficient of a resin insulating layer is larger than the linear expansion coefficients of magnetic substrates (ceramic substrates), which are formed from ceramic materials, e.g., ferrite, internal electrodes, and the like. Consequently, in the case where a temperature change of an electronic component occurs, for example, in the case where heating is conducted for mounting the electronic component, the resin insulating layer expands and shrinks significantly as compared with the magnetic substrate and the internal electrode. As a result, there is a problem in that the internal electrode and the external electrode are peeled off thereby easily causing a poor connection.
In particular, regarding the external electrode, in order to enhance the adhesion to a magnetic substrate, nickel (Ni), a nickel-chromium alloy (NiCr), chromium (Cr), and the like are used as the materials for a substrate layer. However, the linear expansion coefficients of these materials for the substrate are small as compared with that of the resin and, therefore, poor connection between the internal electrode and the external electrode tends to occur easily along with temperature changes.
Furthermore, in the case where a coil component is formed as the electronic component, as described in the above-mentioned Japanese Unexamined Patent Application Publication No. 8-203737, it is necessary that the distance between the two magnetic substrates is minimized in order to obtain good electric characteristics, e.g., an improvement of inductance. Consequently, each of the thickness dimensions of the resin insulating layer, the coil pattern (e.g., electrode pattern), and the internal electrode is made small. As a result, the thickness dimension of the exposed end surface of the internal electrode is on the order of several micrometers and, therefore, is very small such that the internal electrode and the external electrode tend to peel off easily.
On the other hand, the above-mentioned Japanese Unexamined Patent Application Publication No. 2006-287063 discloses a configuration in which the connectivity between the internal electrode and the external electrode is enhanced by disposing a conductor pad on the end surface of the laminate. However, along with progression of miniaturization and a reduction in profile of the electronic component, the end surface area of the internal electrode and the end surface area of the external electrode have become very small. Consequently, it is difficult to form a conductor pad having a predetermined area accurately. Furthermore, it is necessary to add a new step in order to form the pad and, therefore, there is a problem in that the productivity is reduced.